Won't decode specialized base64 encoded histogram data properly

[graefen]

This depends on Node Buffer functionality for base64 decoding. I used this as a shim to provide that functionality in the browser: https://github.com/feross/buffer (I used the standalone version.)
Seemed to work, but decoding is not working properly. With these combined, I tried decoding AAFE+wAB I got { bvs :[{ bucket:{val:68,exp:251},count:1 }]} which is wrong; it's supposed to decode as { bvs :[{ bucket:{val:68,exp:-5},count:1 }]} because the exponent needs to be a signed 8bit int.